Apparatus for the production of pressed board

ABSTRACT

An apparatus or plant for making pressed board from particulate or fibrous material, comprises a dispensing station for depositing such material on a movable surface, e.g. a conveyor and/or tray, a prepress for compacting the mat of this material and a multiplaten press for the final pressing stage. The prepress has at least two stages and is operated to compact the mat in these stages alternately, i.e., one mat is compacted in one stage of the prepress while a previously compacted mat is removed from the other stage and a new layer of the material introduced therein by alternatingly operable service mechanisms for charging and discharging the prepress.

United States Patent [191 Axer et al.

[111 3,824,058 [451 July 16,1974

1 1 APPARATUS FOR THE PRODUCTION OF PRESSED BOARD [75] Inventors:Heinrich Axer, Nettetal-Lobberich;

Ernst Heckmanns, Straelen, both of [21] Appl. No.: 321,796

[30] Foreign Application Priority Data 425/339, 455, DIG. 200, 327, 406;100/195, 196, 199, 137, 207, 140, 209

[5 6] References Cited UNlTED STATES PATENTS 1,883,887 l0/l932 Farley100/196 2,878,728 3/1959 Clark .I 100/196 2,883.705 4/1959 Hartley100/196 X 2,923,030 2/ l960 Himmelheber et al. 425/80 X 3,173,976 3/1965Paerels et al. 425/455 X 3,428,505 2/l969 Siempelkamp.

Hutz 425/DlG. 200

Primary ExaminerRobert L. Spicer, Jr.

Attorney, Agent, or Firm-Karl F. Ross; Herbert Dubno 5 7] ABSTRACT Anapparatus or plant for making pressed board from particulate or fibrousmaterial, comprises a dispensing station for depositing such material ona movable surface, e.g. a conveyor and/0r tray, 21 prepress forcompacting the mat of this material and a multiplaten press for thefinal pressing stage. The prepress has at least two stages and isoperated to compact the mat in these stages alternately, i.e., one matis compacted in one stage of the prepress while a previously compactedmat is removed from the other stage and a new layer of the materialintroduced therein by alternatingly operable service mechanisms forcharging and discharging the prepress.

.10 Claims, 7 Drawing Figures L av r 111 3c 3a PAIENIEuJuL 1 81974 SHEET2 BF 4 APPARATUS FOR THE PRODUCTION OF PRESSEI) BOARD FIELD OF THEINVENTION The present invention relates to the production of pressedboard and, more particularly, to an apparatus, plant or installation forthe manufacture of pressed board from fibrous or particulate materials.

BACKGROUND OF THE INVENTION Numerous systems have been providedheretofore for the production of pressed board of various properties orcharacteristics. The term pressed board is intended to be generic to theboards or sheets made from fibers or particulate materials of varioustypes, with or without externally supplied binder, and having a widevariety of properties. For example, fibrous materials consistingpredominantly of cellulose can be compacted to provide a low-densityboard with high porosity for use as a thermal or acoustical insulation,using a minimum of binder. By contrast, highly compacted wood-fiber,sawdust or chipboard can be made with a high density for use asstructural materials. The board may have still higher density when, inplace of or in addition to the naturally occurring abietic resins,thermally activated resins or thermally hardening resins of thephenol-formaldehyde, resorcinol or urea-type are supplied. The productmay have a smooth or rough finish, may be water-permeable or imperviousto gases and moisture-may be provided with an aesthetically pleasingsurface or with natural wood-grain appearance. The properties of theproduct may be modified by using facing layers of relatively finecomminuted materials and a core layer of a relatively coarse mate rialetc. All such products can be denoted, for the purposes of the presentinvention, as pressed board.

In general, pressed board may be produced by depositing a layer or matof noncoherent or loosely coherent material, with or without suchbinders as have been mentioned above, upon a surface, subdividing thelayer and/or trimming it into rectangular configuration, and pressingthe layer with or without heating (preferably with heating) between theplatens of a platen press. It is a common practice to provide, for thispurpose,-a multiplaten press consisting of a plurality of verticallyspaced heated platens, a press-closure device for simultaneously movingthe platens together and a fluidresponsive system, e.g. a hydrauliccylinder, to compact the platens betwen a head plate and a bed plate.

On the charging side of the press there may be provided a multilevelrack capable of depositing the layers or mats upon the respectiveplatens while, at the exit side of the press, another rack is providedto receive the pressed board and advance it to further processing, e.g.to a curing or tempering kiln.

Between the charging rack and the mechanism for dispensing thecomminuted material, e.g. wood fibers, sawdust or wood chips, there iscustomarily provided a prepress which operates in the cadence of advanceof the mats to compact each mat or layer and impart a greater coherencyto the latter while leveling the layer so to improve the effectivenessof the final press operation and the ability to handle the mat.

A typical installation for the manufacture of pressed board, especiallychipboard, fiberboard and the like,

paratus for producing particle board, fiberboard or the comprises adispensing station at which the mat or layer rack, a prepress forprecompression of the layers being provided along this path.

A prepress of the latter type, of course, may operate in the cadence ofadvance of the layers or mats as already indicated and it is even knownto provide multiplaten prepresses upon which the mats are deposited .forsimultaneous compaction. A key problem with such systems is that all ofthe press stages must open and close simultaneously and thus the pressstroke must await deposition of a layer or upon each of the prepressstages. Thus if the time required for formation of a mat or layer of acertain length is represented as A t and there are x stages of theprepress, the press must remain open for a period at least equal to x Atbefore precompression can commence. The press cycle is thus greater thanx A t. To eliminate this lag in the operation of the production line, itis possible to provide a charging rack ahead of the prepress so that themats can accumulate while the press is closed'and then charge all of theplatens when the press reopens. Apart from the fact that a charging rackof this type adds significantly to the cost of the system, it will beapparent that the press stroke cannot be less than x A t.

Furthermore, most conventional dispensing systems are able to adjust thethickness of the layer deposited (e.g. to vary the thickness of thefinal pressed board) only by varying the rate at which the receivingsurface is moved past the dispensing device. Thus the receiving surfacemust be slowed to increase the thickness of the deposited layer, therebyincreasing the duration A t. For the thick pressed board, therefore, theprepress cycle is increased in duration. It will be noted also that,when all of the platens of the prepress are to be closed simultaneously,the hydraulic device used for this purpose will have a stroke equal tothe product of x and the displacement of each platen so that additionaltime is required for a greater number of platens of the pre-' press. Themechanical and hydralic dead time of the press and its recycling timeare comparatively large. This is the case whether or not the layers ormats are moved on carrying trays through the system or are displaced byconveyors (e.g. conveyor tablets) therethrough. I

To avoid some of these disadvantages, it has been proposed to increasethe number of platens and thereby reduce the dead time per mat or layer.This has been found to be unsatisfactory as well and increases thecapital cost of the installation.

OBJECTS OF THE INVENTION It is the principal object of the presentinvention to provide an improved apparatus, plant or installation forthe production of pressed board whereby the aforementioned disadvantagescan be obviated.

It is another object of the invention to provide an aplike with aprepressing stage having a short stroke time and recycle period.

SUMMARY OF THE INVENTION These objects and others which will becomeapparent hereinaftenare attained, in accordance with the presentinvention, in a plant or apparatus for the productionof pressed boardhaving a prepress of the multiplaten type with at least twoalternately'actuatable platens individually shiftable to compactrespective mats or layers during alternate half cycles of the prepressoperation.

According to a more specific feature of the invention, the apparatus forthe production of pressed board comprises a dispensing station forforming a succession of mats or layers of noncoherent or limitedlycoherent material, a multiplaten main press downstream of the dispensingstation, a charging rack immediately upstream of the main press and adischarge rack or device immediately downstream of the main press, andassociated conveyors for advancing the layers from the dispensingstation to and through the main press. Along the path between thedispensing station and the main press, there is provided according tothe present invention a multiplaten prepress which, advantageously, hasfewer press stages than the main press and is provided at its upstreamand downstream sides with respective service devices for inserting thelayers into thr prepress and removing it therefrom.

The invention principally resides in that the multiplaten prepress isanalternate-stroke press in which the plates move in opposite directionsduring respective half cycles of the press operation, the servicedevices likewise being operated to alternately dispose a layer upon atleast one press platen during onehalf of the prepress cycle and upon theother platen during the second half of the press cycle, the dischargedevice being operated inversely to the feed device so that the presslayers may be removed.

The invention makes use of the fact that a singlestage press canoperate, for mechanical and hydraulic reasons, with a very short strokeor recycle period, so that the multiplaten press thus becomes anassembly of single-stage presses.

According to another feature of the invention, the multiplaten prepressis a two-stage press having a fixed central platen or bed against whicha movable upper platen and a movable lower platen can be urged inopposite directions-by mechanical or hydraulic platen displacementmeans, the latter means being alternately operable for shifting therespective platens. The fixed central bed or platen preferably lies inline with the conveyor paths mentioned earlier.

With a two-stage prepress, according to the invention, the plant isgreatly simplified, especially when the charging and discharging servicedevices each include two service stages respectively alignable with theplatens of the prepress at least in the open position of the respectiveplaten, at least one service stage being vertically shiftable for thispurpose. The service stages may be conveyor tablets, swingable platformsor the like, or swingable platforms may be provided ahead of or behindeach service rack in the direction of travel of the layers forpositioning the latter on the respective layers. The service devices canbe provided with belt conveyors which are shiftable by means ofparallelogrammatic lankages and can be inserted into the differentlevels of the two-stage prepress.

According to the principles of this invention, the transport means inand adjacent the prepress are constituted by conveyor belts and, wheresupport or carrying trays are not provided for the layers, the conveyorDESCRIPTION OF THE DRAWING The above and other objects, features andadvantages of the present invention will become more readilyapparentfrom the following description, reference being made to the accompanydrawing in which:

FIG. 1 is a somewhat diagrammatic elevational view illustrating a plantfor the production of pressed board according to the present invention;

FIG. 2 is a detail view, greatly enlarged, of the region illustrated atII of FIG. 1',

FIG. 3 is a cross-sectional view taken along the line III III of FIG. 2;

FIG. 4 is a detail view of the region IV of FIG. 2 but illustratinganother embodiment of the invention;

FIG. 5 is a view similar to FIG. 1 of the charging side of the prepressaccording to another embodiment of the invention;

FIG. 6 is a view similar to FIG. 5 illustrating still anotherembodiment; and

FIG. 7 is a detail view of another press charging device ahead of theprepress according to the present invention.

SPECIFIC DESCRIPTION In FIGS. 1 3, we have shown an apparatus for theproduction of pressed board which comprises a dispensing station 2having a plurality of hoppers 3 offset one behind the other in thedirection of travel (arrow A) of the material adapted to form thepressed board 1. The hoppers 3 are provided with the usual dispensingheads 30!, 3b and 30 for respectively depositing a layer of fineparticles, a layer of coarse particles and another layer of fineparticles upon a conveyor 30! to form a layer 14 which may be subdividedtransversely to the direction of movement to form respective mats orlayers. I

At the other end of the production line, there is provided a multiplatenpress 4, represented diagrammatically in the drawing and preferably ofthe type described in commonly assigned US. Pat. No. 3,050,777 and3,209,405. The dispensing devices 3, 3a, 3b and 30 as described incommonly owned US. Pat. No. 3,282,767, the layers being trimmed andshaped as described in US. Pat. No. 3,051,219, 3,096,227 and 3,428,505.The conveyor 3d may be of the type described in commonly owned US. Pat.No. 3,224,758.

Flanking the press 4, there are provided a charging rack 5 and adischarging rack 6 which may be formed with conveyor tablets orconveyor-band tablets for advance of the pressed board or the layers(see U.S. Pat. No. 3,565,725).

Between the multiplaten-press charging station 5, which operates asdescribed in US. Pat. No. 3,565,725, and the layer-forming station 2,there is provided a conveyor arrangement which includes a two-levelplaten press 8 (i.e., the prepress) and means for charging anddischarging this prepress (i.e., the service devices for the prepress)together forming part of the transport path.

At the upstream of the prepress 8, i.e., between the conveyor 3d and theprepress, there is provided a charging device 9 while a dischargingdevice 9' is provided between the prepress and the charging rack 5.

The two-level prepress 8 is an alternate-cycle press which is shown inan open condition in FIGS. 1 and 2. More particularly, the press 8comprises a fixed central bed 10, preferably in line with the conveyor3d and the general transport path, which is mounted in a frame 10a andcarries an upwardly facing heated or unheated bed plate 10b and adownwardly facing heated or unheated bed plate 10c. J uxtaposed withthese platens are an upper platen 11 carried by the pistons 11a of ahydraulic cylinder arrangement 11b schematically shown in FIG. 3, whilea lower platen 12 is carried by pistons 12a of cylinders 12b formovement toward and away from the plate 100. r

The press platens 11 and 12 are thus shiftable independently of oneanother and in alternate half cycles, the charging device 9 and thedischarging 'device 9 likewise operating in alternation to feed anddischarge the two-stage prepress 8.

The charging device 9 comprises a pair of conveyorband tablets (see US.Pat. No. 3,565,725), of which at least the upper one is verticallymovable while the discharge device comprises conveyor-band tablets 7,the upper member of which is vertically displaceable. The stages of thepress can be provided with conveyor belts 20 for advancing the layersinto and out of the press.

The system of FIGS. 2 and 3, shown to use presscharging trays, operatesas follows:

A prepressed slab 13 of the comminuted material lies upon the lowerpress platen 12 and, when its conveyor 20 is driven, carries the slab 13onto the lower conveyor 7 of the discharge device 9'. The conveyors 20may be driven or undriven and, in the latter case, the prepressed bodymay be shifted from the prepress by the introduction of a new layer 14upon its charging tray 19. During this period, the upper press platen l1closes to compact the layer 14 therein, the previously discharged body13 being carried by the upper conveyor 7' of the discharge device 9 inthe direction of arrow B, the conveyor carrying member 13 having loweredfrom the dot-dash position previously. The upper stage 15 of chargingdevice 9 is, during this period, provided with a new layer 14 as thelayer 14 of the lower stage 17 is advanced into the press.

When the upper stage 16 of the press opens, the alternate half-cyclecommences, i.e., the platen l2 closes to compact the new layer 14deposited thereon. The lower conveyor 7' of the discharge device 9'rises into alignment with the upperconveyor and the prepressed layer ofthe upper stage 16 is deposited upon this conveyor of the dischargedevice. Meanwhile, the conveyor 15, in its upper position, deposits alayer 14 of uncompacted comminuted material in the upper stage 16.

In the embodiment illustrated in FIGS. 1 3 the service devices 9 and 9are provided with conveyor-belt stages, the belts 18 of which are drivenalternately in the previously described pattern with automatic orprogramming means of conventional construction.

When a charging plate 19 is not used, the conveyors may have theconfiguration shown for the conveyor 21 6 of FIG. 4, i.e., the conveyormay have a transfer blade 22 which can be shifted from the right to theleft to overlie the conveyor 20 and deposit the mat 14 thereon smoothlyand uniformly (see US. Pat. No. 3,565,725).

In FIG. 5, we show a modification in which the dispensers 103 of thedispensing station 102 deposit the layer 114 of comminuted material upona conveyor 103d for subdivision into mats, as previously described butnot here illustrated. Ahead of the charging device 109, provided withconveyors 107, as previously described, there is provided a swingingplatform or tipple 109a which can deposit the mats selectively upon theconveyor belt 107. The charging device 109, of course, is operated inthe manner previously described to feed the mats alternately to thelower press platen 112 or the upper press stage 116 of the prepress 108.

In the modification of FIG. 6, the swinging platform 209a is providedbetween a conveyor and the press, the system otherwise being similar tothat of FIG. 1. FIG. 7 shows that the conveyor tablets 307 can beprovided with a parallelogrammatic linkage 3070 for movement into andout of the prepress to deposit the mats therein.

The improvement described and illustrated is believed to admit of manymodifications within the ability of persons skilled in the art, all suchmodifications being considered within the spirit and scope of theinvention except as limited by the appended claims.

We claim:

1. An apparatus for the production of compressed board, comprising: I

a dispensing station for forming layers of a comminuted material;

a multiplaten main press spaced from said dispensing means;

means for charging said multiplaten press with a plurality ofprecompacted layers;

means for discharging finely compressed layers from said press;

a multilevel prepress between said dispensing means and said means forcharging said press, said multilevel prepress having alternatelyoperable stages for compacting respective layers therein;

a charging device upstream of said prepress alternately feeding layersfrom said dispensing means to said stages; and

a discharge device downstream of said prepress for recoveringrecompacted layers from said stagesaltemately and advancing same to saidmeans for charging said press.

2. The apparatus defined in claim 1 wherein said prepress comprises astationary intermediate bed, an upper press platen overlying said bedand defining a stage between itself and said bed, a lower press platendisposed below said bed and defining a lower stage between itself andsaid bed, and independently operable but alternating drive meansconnected to said platens.

3. The apparatus defined in claim 2 wherein at least one of said devicescomprises at least one conveyor, said bed being disposed at the level ofsaid conveyor.

4. The apparatus defined in claim 2 wherein each of said devicescomprises a pair of stacked conveyors, at least one conveyor of eachstack being shiftable vertically.

5. The apparatus defined in claim 2 wherein at least one of said devicescomprises a swingable platform for changing the level of a layerdisplaced therealong.

6. The apparatus defined in claim 2 wherein at least one of said devicescomprises a pair of belt conveyors comprising a pair of stackedconveyors, one of said conveyors lying at the level of said low platenin an open condition of the lower stage of said multilevel prepress,said upper platen being shiftable vertically to the level of the uppersurface of said bed.

9. The apparatus defined in claim 8 wherein each stage of said press isprovided with a respective endless conveyor for advancing said layersthrough said press.

10. The apparatus defined in claim 9 wherein said discharge devicecomprises a pair of stacked conveyors at least one of which isvertically movable.

1. An apparatus for the production of compressed board, comprising: adispensing station for forming layers of a comminuted material; amultiplaten main preSs spaced from said dispensing means; means forcharging said multiplaten press with a plurality of precompacted layers;means for discharging finely compressed layers from said press; amultilevel prepress between said dispensing means and said means forcharging said press, said multilevel prepress having alternatelyoperable stages for compacting respective layers therein; a chargingdevice upstream of said prepress alternately feeding layers from saiddispensing means to said stages; and a discharge device downstream ofsaid prepress for recovering recompacted layers from said stagesalternately and advancing same to said means for charging said press. 2.The apparatus defined in claim 1 wherein said prepress comprises astationary intermediate bed, an upper press platen overlying said bedand defining a stage between itself and said bed, a lower press platendisposed below said bed and defining a lower stage between itself andsaid bed, and independently operable but alternating drive meansconnected to said platens.
 3. The apparatus defined in claim 2 whereinat least one of said devices comprises at least one conveyor, said bedbeing disposed at the level of said conveyor.
 4. The apparatus definedin claim 2 wherein each of said devices comprises a pair of stackedconveyors, at least one conveyor of each stack being shiftablevertically.
 5. The apparatus defined in claim 2 wherein at least one ofsaid devices comprises a swingable platform for changing the level of alayer displaced therealong.
 6. The apparatus defined in claim 2 whereinat least one of said devices comprises a pair of belt conveyorsinterconnected by a parallelogrammatic linkage.
 7. The apparatus definedin claim 2 wherein at least one of said devices is formed with aconveyor having a discharge blade adapted to be withdrawn over anotherconveyor to deposit a layer upon the latter without distortion.
 8. Theapparatus defined in claim 2 wherein said dispensing station is providedwith a first conveyor belt adapted to advance said layers, said chargingdevice comprising a pair of stacked conveyors, one of said conveyorslying at the level of said low platen in an open condition of the lowerstage of said multilevel prepress, said upper platen being shiftablevertically to the level of the upper surface of said bed.
 9. Theapparatus defined in claim 8 wherein each stage of said press isprovided with a respective endless conveyor for advancing said layersthrough said press.
 10. The apparatus defined in claim 9 wherein saiddischarge device comprises a pair of stacked conveyors at least one ofwhich is vertically movable.